Spark plug tester



May 3, 1938. E. s. HOLM El AL SPARK PLUG TESTER Filed Nov. 50, 1957 2 Sheets-Sheet 1 MAGNETO GROUND HIGH TENSION PRIMARY :mvzsr s. HOLM BY LESTER A. MILLER ATTORNEY May 3, 1938. E. s. HOLM El" AL I SPARK PLUG TESTER 2 Sheets-Skeet 2 Filed Nov. 50, 19:57

INVENTORS ERNEST S. HOLM BY LESTER A. -MILLER ATTORNEY plugs and which tests the plugs with the plug vided with oil grooves 28. Apiston rod 23 secured 35 vention, and

Patented May 3, 1938 I 2,115,719

UNITED STATES PATENT' OFFICE- 2,115,719 SPARK PLUG rnsrnn Ernest s. HoIm and Lester A. Miller, Quincy, Mass. 1 Application November 30, 1937, Serial No. 177,283

' 11 Claims. (01. 175-183) (Granted under the act of March 3, 1883, as.

amendedApril 30, 1928; 370 0. G. 757) This invention relates to a spark plug tester, Wardly by acompression coil spring 25 located and has for an object to provide an improved between the bottom of the piston and alower cylspark plug tester, which, with suitable adapters, inder head 26. An oil reservoir 21 connects into is capable of use with all types and sizes of spark the cylinder chamber 23, the piston being propoints under pressure conditions simulating the to the bottom of piston 24 extends through an pressure under which the plug is to be used. opening in the lower cylinder head 26. A spark A further object of this invention is to provide plug clamp 30 is pivoted to the rod 29 by the pin a spark plug tester which may be operated very 3|, a curved surface 32 permitting the clamp 30 quickly both in placing the plug in testing posito pivot to the dash line position 30' against the 1 tion and in removing it therefrom, as well as in c a p c Sp 33 When e cam 34 Strikes th automatically providing that the predetermined pins 35 set in cylinder head Has a result of up-. minimum pressure will be present at the points ward movement of piston rod 29. A key 36 exwhen the test. takes place. tending into a recessed groove 31 in the piston A further object of this invention is to provide rod 29 holds the clamp 30 from accidentally 15 a plug testing device which is fullyautomatic rotating.

except for the manual'operation of inserting and With the construction just described, the cl m removing the spark plug and turning the con- 30 will go to position 30 when the compression trol valve handle. coil spring hasraised the piston to the top- A further object of this invention is to provide most position (not shown) and to the position a spark plug tester which eliminates, danger of when compressed air enters cylinder chamber injury to the operating personnel since theopera- 3 and moves t do nw rdlytor does not look directly through a glass window A Spark pl to be tested, is placed on the into the compressed air chamber and the comrubber gasket 39 and has its points extended into 25 bustion recess of the firing plug, but rather sees the firing cha b r 40. S Wil be Obser the 5 the reflected image of the chamber and the wa ls f the spark p ug firin c amb r ar un- .spark int a. reflecting surface. threaded, and are of greater diameter than that With the foregoing and other objects in view, of the spark plug threads 4|, but of less diameter the invention consists in the construction, cor'nn t at f he flange Skirt w c s s 3o bination and arrangement of parts,-as will be deon the gasket 39. The bottom of the firing 30 scribed more fully hereafter. I chamber 40 is closed 01f by a heavy explosion In the drawings: proof transparent panel 43 secured thereto by Fig. 1 is a partly diagrammatic and partly seca gland 44 between rubber gaskets 45. Set in the tional view of the spark plug tester of this inbase l0 below t e panel 43 is a' o .w ch

' may be a chromium plated metal sheet, at a- Fig. 2 is a front elevational view. suitable angle, such as 45 degrees, so as to be The spark plug tester of this invention consists easily observable by an operator in front of the of a gooseneck frame l0 securely mounted on a S erhollow base II. A manual control handle l2 A spark pl adapt uita l -f r th parhaving a pointer 13 adapted to indicate either ticular type and size of spark plug 38 being tested, 4 the on position It or the On position is is is plac d n th p 38 s as t c m twe n it mounted .on a connecting rod is extending d th lamp 30 as it m v s f om p sition 30'. through the base II to a two-way valve [1. This This adapter is made of insulation material and v valve l'l connects a tubing id to a source of oomcarries a contact wire 48 whose lower end abuts pressed air through the tubing I9 when the against the spark p u Contact Stem e pp 45 pointer I 3 is in the "On position i5, and when end 50 abutting against a contact 5| connected in Off position H, the valvel'l shuts off the through an u a or 5 o a high tension tertubing l9 and -connects the tubing is to an exminal 53. haust port 20 to the atmosphere. An expansion As the piston 24 is moved downwardly by the 50 chamber 2| connected to tubing l8 acts as a c mp air to the Position ShDWh, causing e 60 .cushion to the flow of compressed air through clamp 30 to'engage the plug 38, a port 54 is untubing I 8. covered in the side of cylinder chamber 23 and The tubing i8 connects through a cylinder headallows compressed air to enter through duct 55 22 "into a cylinder chamber 23 in which is 10- to the spark plug firing chamber 40, which is 55 cated a vertically movable piston 24 urged upnow sealed by the plug 38 under the clamp 30. 55

' per diaphragm chamber 59 above a diaphragm 50' within the diaphragm housing 6|. A diaphragm plate 62 on 'the bottom of diaphragm 60 abutsagainst a pin 53 which is pressed thereagainst by a coil spring 54., The strength of this coil spring 64 may be adjusted by partially unthreading the support 55, or by.substitutlng another spring of the desired' strength. The lower end of pin 53abuts against 'a spring arm 58 carrying a contact 51 and adapted to moveit to circuit breaking position with relation to contact 58.

The contact 63 is connected by a conductor 69 to the primary 10 of a magneto 1| continuously driven by a separate electric motor (not shown). The high tension 12 of magneto II is connected by a conductor 13 to the high tension terminal 53,- while the magneto ground I4 is connected by conductor 15 to the gooseneck frame .lll at any convenient position; as shown.

As the air pressure flows from the cylinder chamber 23 to both the firing chamber 40 and to the diaphragm chamber 59, it compresses diaphragm coil spring 94 until the pin 53 breaks the circuit from the primary 10 through conductor 69 and contacts 68 and 61 to the ground through base'll and gooseneck frame ID to conductor 15 and magneto ground 14. This circuit break does not take place until the requisite pressure is present in chambers 40 and 59, as determined by diaphragm spring 64 and measured by air gauge 51. The high voltage induced in the secondary then necessarily'causes a current to flow from ground through the clamp 30 to plug skirt 42 and across the spark gap of the spark plug points within chamber 40 and through the plug stem 49 to the high tension terminal 53 and high tension con- ,ductor I3 to the high tension terminal 12 of the magneto H.

In operation, the spark plug to be tested is placed on the gasket 39 with its plug points within the firing chamber 40.- The adapter 41 is then placed on the spark plug and the operator moves handle l2 to place pointed in theOn position l5. The valve I! then allows air to flow through tube 18, which air is cushioned by chamber 2|, and moves a piston 24 downwardly compressing spring 25 and allowing spring 33 to move clamp 39 from position 30 toward position 30 as thecam surface isrelieved of pressure on the pins 35. When the clamp'reaches position 30, contact 50 on adapter 41 presses against contact to complete the electrical path from plug stem 49 through contact wire 48 to the high tension terminal 53 and conductor I3, the port 54 becomes uncovered by the'piston 24, and allows pressure to build up through duct 55 to firing ,chamber 40 and diaphragm chamber 59; When the pressure in these chambers has built up to the predetermined amount, as controlled by spring 64, the primary circuit is broken by the separation of the contacts 68 and 61, inducing a high voltage in the secondary which causes the current to flow across the gap between the spark plug points through the high tension conductor 13 to the high tension terminal in the magneto.

The operator, standing in front of the tester, observes the firing through the reflector 46, reading the air gauge 51 to be sure that the plug fires properly under the desired pressure. After finthe testing of the plug 38, he moves the handle l2 to bring the pointer l3 to the Oil' position 14, pressure from tube l9 and allows the pressure in chambers 40, 59 and 54 to.escape,through exhaust port 20 to the atmosphere. The piston 24 then moves upwardly under the force of spring 25, moving the clamp 30 to position 30' allowing the tested plug 38 to be removed and replaced by another plug to be tested. With the new plug to be tested in positionwith. its adapter on the gasket 39, the control handle I2 is moved to place the pointer l3 in the on position [5, opening valve I! from tube H! to tube l8 and cutting ofi exhaust port 20, thus repeating the cycle. The presence of expansion chamber 2| cushions the operation of clamp 39 as it moves against the plug 38.

Other modifications and changes in the proportions and arrangements of the parts may be made by those skilled in the art without departing from the nature and scope of the invention, as defined in the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

Having thus set forth and disclosed the nature of this invention, what is claimed is:

' 1. In a spark plug tester, a compression chamber having an open end, a compressible gasket positioned in the chamber wall at said open end, a clamp for pressing a flange of a spark plug firmly against said gasket when the threaded end of the plug is inserted in said chamber to provide a substantially pressure-tight junction between the flange and the gasket, and pressure operated means for operating said clamp.

2. In a spark plug tester, a compression chamber having an open end, a compressible gasket positioned in the chamber wall at said open end, a clamp for pressing a flange of a spark plug firmly against said gasket when the threaded end of the plug is inserted in said chamber to provide a substantially pressure-tight junction whereupon the valve ll cuts off the 3. In a spark plug tester, a compression chamber having an open end, a compressible gasket positioned in the chamber wall at said open end, a clamp for pressing a flange of a spark plug firmly against said gasket when the threaded end of the plug is inserted in said chamber to provide a substantially pressure-tight junction between the fiange and the gasket, and pressure operated means for operating said clamp, supplying pressure to said compression chamber, and causing a high tension circuit to flow across the plug points within the chamber when the pressure within the chamber has reached a predetermined minimum.

4. In a spark plug tester, a compression chamber having an open end, a compressible gasket positioned in the chamber wall at said open end,

a clamp for-pressing a flange of a spark plug firmly against said gasket when the threaded end of the plug is inserted. in said chamber to provide a substantially pressure-tight junction between the flange and the gasket, and pressure operated means for operating said clamp, supplying pressure to said compression chamber, and means for cushioning the operation of said clamp.

5. In a spark plug tester, a compression chamber having an open end, a compressible gasket positioned in the chamber wall at said open end, a clamp for pressing a flange of a spark, plug firmly against said gasket when the threaded end of the plugis inserted in said chamber to provide a substantially pressure-tight junction between the flange and the gasket, and pressure operated means for operating saidclamp, sup plying pressure to said compression chamber, means for cushioning the operation of said clamp, and means for moving said clamp to plug holding and plug releasing position.

'6. In a spark plug tester, a compression chamber having an open end, a compressible gasket positioned in the chamber wall at said open end,

clamp to plug holding'and plug releasing posi-' tion.

'7. A spark plug testerucomprising, in combination, a base,,-a compression chamber having an open end in said base, a compressible gasket in the chamber wall at said open end, adapted to supporir'the skirt of a spark plug to be tested with the plug, points within the chamber, a frame mounted on said base overhanging said chamber, a sparkplug clamp movably mounted on said frame, and pressure means for actuating said clamp to clamping position.

8. A spark plug tester comprising, in combi-.

nation, a base, a compression chamber having an open end in said base, a compressible gasket in the chamber wall at said open end, adapted to support the skirt of a spark plug to be tested with the plug points within the chamber, a frame mounted on said base overhanging said chamber, a spark plug clamp movably mounted on said frame, and pressure means for actuating said clamp to clamping position, and supplying pres sure to said compression chamber.

9. A spark plug tester comprising, in combination, a base, a compression chamber having an open end in said base, a compressible gasket in the chamber wall at said open end, adapted to a support the skirt of a spark plug to be tested with the plug points withinthe chamber, a frame mounted on said base overhanging said chamber,

a spark plug clamp movably-niountedon said frame, and pressure means for actuating said clamp to clamping position and supplying pressure to. said compression chamber, and causing a high tension circuit to flow across the plug' points within the chamber when the pressure within the chamber has reached apredetermined minimum. I I

10. A spark plug tester comprising, in combination, a base, a compression chamber having an open end in said base, a compressible gasket in the chamber wall at said open end, adapted to support the skirt of a spark plug to be tested with the plug points within the chamber, a-frame mounted on said base overhanging said chamber, a spark plug clamp movably mounted on said frame, pressure means for actuating said clamp to clamping position and supplying pressure to said compression chamber and causing a high tension circuit to flow across the plug points within the chamber when the pressure within the chamber has reached a predetermined'minimum, and means for cushioning the operation of said clamp.

11. A spark plug tester, comprising, in combination, a base, a compression chamber having an open endin said base, a co mpressible gasket in the chamber wall at said open end, adapted to support the skirt of a spark plug to be tested with" the plug points within the chamber, a frame mounted on said base overhanging said chamber, a spark plug clamp movably mounted on said frame, pressure means for actuating said clamp to clamping position andsupplying pressure to said compression chamber, means for cushioning the operation of said clamp, and means for moving said clamp to plug holding and plug re- ERNEST S. HOLM. LESTER A. MILIER.

leasing position. 

